I guess this is the scenario I’m thinking of: “With a Librem Key linked to your encrypted drive, you can boot your system, insert your key, and enter your PIN when prompted. You can always fall back to your passphrase if your Librem Key isn’t at hand.
Just remove your Librem Key and your desktop will lock automatically, protecting your system from snooping while you are gone.”
I don’t get the ‘power injector’ comments. My scenario has the Librem Key plugged into the Librem 5, and a USB power supply plugged into the other end of the Librem Key. Unplug the power supply, the phone stops charging, but the Librem Key still works. Plug in the power supply the phone starts charging. Maybe I’m underestimating the complexity of USB PD.